The present invention generally relates to digital multimedia distribution systems and more specifically to digital transmission of encrypted multimedia content over an unsecured connection.
Providers of multimedia content can digitize content for distribution via digital communication networks. An important issue faced by a content distribution system is enabling only those customers that have purchased the content to play the content and compartmentalize access to all the stakeholders in the content distribution chain. One approach is to encrypt portions of the content and to issue encryption keys to authorized users that enable encrypted portions of the content to be unencrypted. Layers of keys and protection policies can be used so a single encryption key alone is insufficient for the user to access the content. In a number of systems, users purchase players that possess specified decryption capabilities. Content providers can distribute content to user's owning such a player in an encryption format supported by the player. Complying with a specified protection policy typically involves using an encryption key specified by the manufacturer of the players. In many instances the manufacturer of the players will not reveal the encryption keys used in the specified encryption scheme and likewise the content provider does not want to share the content keys to the manufacturer of the players.
Communications between components or processes of players or playback systems are typically trustworthy and secured. However, when communication or the transporting of information becomes unsecured or untrustworthy, such gaps need to be accounted for and filled. This has become more evident with advent and popularity of open multimedia frameworks. Bi-directional communication requirements and/or run time challenges and authentication requests to fill such gaps have proved to be less than adequate.
There are many ways of securing communication, including ciphering and encryption.
Ciphering is a procedure used to secure data that typically involves using a series of steps to scramble and render the data readable only to the intended audience. The procedure itself does not require an outside source, such as a key, in order to encipher or decipher the data. Rather, data can be properly deciphered by the intended audience so long as deciphering exactly follows the enciphering steps to unravel the data. Encryption is a procedure used to secure data. That typically involves the use of an external input for at least one step in the procedure, such as a key, in order to secure and/or access the data. The external data is used to intentionally manipulate at least one step in the encryption or decryption process, changing the way the data processing for encryption occurs. Generally, without the external data or a corresponding decryption key in an encryption process, a step in a corresponding decryption process cannot properly be executed and the data cannot be properly decrypted.
In the context of digital media, encoding is a procedure by which digital media is represented in a digital format. The format is typically selected to obtain specific benefits during the transportation, playback and storage of the digital media format used. For example, representing the media using fewer bits may be beneficial to transfer data in order to minimize bandwidth usage or storage space. In another example, a media player may only decode or read media in a certain format and therefore the digital media may first be in that format in order to be decoded by that media player.
Decoding is a procedure by which digital media in a format is translated into a format readable by a media player for rendering on a display device. Often, decoding may also reverse processes associated with encoding such as compression. In instances where encryption and/or enciphering have been applied to encoded media, the enciphering process or encryption process typically must be reversed before the encoded media can be decoded.